During tests of transmitting files over a single optical fiber channel between Kyoto and Osaka aimed at simulating vibrations and possible obstacles likely to occur in actual operation, a optical telecommunications system developed by Japanese OKI Electric has reached a data transmission rate of 160Gbps. OKI transmitted four 40Gbps signals on one channel, and to make this possible OKI reduced the size of the TDM (Time Division Multiplexing) module by two-thirds and cut down signal loss.